The purpose of this investigation is to further examine an antigen(s) found associated with the Wilm's tumor (nephroblastoma). One antigen has been found by immuno-diffusion to be cross reactive with fetuin, a glycoprotein found in fetal calf serum. This antigen has also been found in in vitro cultures of Wilm's tumor; the WiTu cell line. It is our intent to determine if this antigen as isolated by chelation (EDTA) is related to an antigen reported to be Wilm's associated by other workers using phytic acid and fluorocarbon extraction procedures. We further wish to develop more sensitive methods, other than double-im- munodiffusion, to detect the presence of the antigens in tumors, serum, and in tissue culture. These include radio-immunoassay and autoradiography of immunodiffusion plates. In addition a micro- cytotoxicity assay will be attempted to determine if anti-fetuin serum can be cytotoxic to Wilm's tumor cells in vitro. Affinity column chromatography will also be utilized in an attempt to isolate the antigen in a more highly purified form for subsequent studies. Isoelectric focusing using ampholines in acrylamide gel and in Sephadex columns will be utilized for detailed analysis and finite purification of the Wilm's antigen as well as determining which cross reactive antigenic determinants are present in fetuin subfractions. The goal of these studies is to develop a rapid and sensitive assay for detection of this antigen, leading to eventual study of its uniqueness to Wilm's tumor, or other tumors, or even as to its specificity to tumor tissue per se.